Thanks e23,
I know it's not a good idea, but since my system has been safe, and avast never caught any file, I thought I'd take a chance until a solution turned up. I had read about also including it in a general settings list, but find no such list. The general settings list is only for paths. I did include it now in the behavior shield list also. Plus I made the filename more general than just in windows. I tried again and at this time my tests are working well: creating a new txt file and opening a txt file. Hopefully this means that the other slowdown conditions also won't occur.
My thought about metapad, at least on my system, is that I renamed metapad as notepad and it is in the windows directory. Thus maybe Avast sees it as a program that has taken over the identity of a windows executable.